1. Field
Aspects of the present disclosure relate generally to electronic circuits, and more particularly, to the fabrication of integrated circuits.
2. Background
An integrated circuit is an electronic circuit on a small plate (substrate) and may be found in a wide variety of everyday electronic devices. The substrate of integrated circuits may be composed of various different types of material, such as silicon, gallium-arsenide, and the like. Glass, which has many cost and performance benefits, has also been used as a substrate for certain types of integrated circuits. For example, glass may be used as the substrate on which miniature electrical and optoelectronic devices such as microelectromechanical systems (MEMS) display and radio frequency microelectromechanical systems (RF MEMS) are fabricated. The MEMS and RF MEMS generally include electrical connections through the glass substrate because devices that need to be electrically connected may be located on different sides of the glass substrate. These through-glass electrical connections are desirable because they are shorter than connections that go around the substrate. Shorter electrical connections also provide less resistance and use up less space than longer electrical connections. The through-glass connections are implemented by creating vias or holes running from one side of the glass substrate to the opposite side and coating the side of the vias with conductive material (through via). Further, some vias may facilitate connections between layers in the substrate without going completely through the substrate (blind via).
Methods of creating vias in a glass substrate include sandblasting through the glass, applying laser beams to ablate the glass and constructing the glass with special chemical properties. With respect to the method involving glass with special chemical properties, when areas of the glass are exposed to light those areas turn into etchable material. Subsequently, etchants are used to etch away the etchable material to create vias. These methods, however, have disadvantages. For example, sandblasting may damage the glass and cause localized cracking. The minimum size via achievable by this method is larger than the via size typically desired. With respect to laser, its use is sequential in nature. That is, one hole or a small set of vias are created at a time, which results in a slow process. Finally, the formulation of the glass substrate with special chemical properties that turns it into etchable material when exposed to light usually involves doping the glass with other materials such as metals. This doping is costly and often negatively affects certain other properties of the glass substrate. One example of this negative effect is excessive RF loss.
The importance of the integrated circuits to modern life is reflected by their widespread use, as mentioned above. Coupled with this widespread use is the fact that the fabrication of integrated circuits requires sophisticated machinery, which translates to large capital investments and overall expensive processes. In view of these factors, improvements in techniques used in the fabrication of integrated circuits are particularly desirable.